Unable to repaint over existing paint color in flood fill f

Question

I am using floodfill image package in flutter with the following parameters:

FloodFillImage(
  width: screenWidth.toInt(),
  imageProvider: AssetImage(
      imagePath ?? "lib/assets/images/painting/coloring_activity_1.png"),
  fillColor: _fillColor,
  avoidColor: const [Colors.transparent, Colors.black],
  tolerance: 100,
)

I am able to paint and re-paint using any of the colors. For example, consider the image below, I am able to drop red on the cloud that I have already colored as blue, I am able to drop green on yellow painted squirrel, etc. However, I am not able to repaint the dark green (hex code 0xff114730) cloud even though it is not present in the list of avoided colors. How do I fix this ?